Wood-burning inserts installed by local specialists in Rio Grande Park

Angled side walls and a narrow back wall

Many masonry fireboxes narrow toward the back and lean forward near the top, a shape meant to throw heat from an open fire into the room. An insert body is a rectangle, so those angles decide how deep it can sit and whether its top passes under the throat.

When the back is too narrow for a full-depth fit, some models are made to sit partly forward on the hearth, which then changes the floor protection they need. We sketch the outline of your firebox during the inspection and hold it against the manual's minimum widths so the unit ends up square, level and supported.

Clearances measured from the insert body

Each insert manual carries a clearance table for combustible materials around the unit. The Pacific Insert guide measures from the insert body and gives separate minimums for an adjacent sidewall, a mantel, top facing and side facing, with a drawing of each.

Those numbers apply to your chosen model only, which is why we never quote an installation from a general rule. At the inspection we measure every combustible surface near the opening and compare it with the table, and anything that falls short appears in the estimate with the fix we propose.

• Wood mantel shelf above the opening
• Wood or painted trim at the sides
• A wall that meets the fireplace at a corner
• Shelving or cabinets built beside the hearth

Trim and facing beside the opening

Side facing that stands proud of the fireplace face, such as a wood pilaster or a stone column, is measured separately in most insert manuals. The Pacific guide ties its side-facing clearance to how far the facing projects from the face.

We measure how far each side piece stands out and how close it comes to the opening. Where trim sits inside the clearance, the estimate names it and the change needed, whether that is moving it, replacing it or choosing an insert that allows it.

Keeping the glass clear

Most inserts wash the inside of the glass with a sheet of incoming air. The Travis manual notes that burning unseasoned wood or burning at low rates leads to dirtier glass, especially at the sides.

Dark glass is usually a fuel or air-setting signal, and it is worth reading that way before reaching for a cleaner. We explain how to clean the glass only when the unit is fully cool, which products your manual allows on it, and which habits keep the airwash doing its job.